HIIT vs LISS: Which Form of Cardio is Most Effective?

is the internet’s official high intensity interval training versus low intensity steady state cardio video. I’m gonna give you the breakdown between HIIT and LISS and help you understand which one is better for you and which one is better overall. So we have this constant competition going between the two and quite honestly, it’s a little bit aggravating because to be fully transparent with you, I think that anyone that’s getting out there and getting active and starting to change their life for the better is doing something great and we can’t constantly discount people that are doing HIIT or doing LISS. If they’re out there and they’re doing something and they’re trying to get healthier, kudos to them, but let’s break down the science, let’s break down the research, and let’s understand the physiology of what’s actually happening in the body.

The first one that I want to look at is LISS, low intensity steady state cardio. This is the cardio that you know. This is the cardio that you’re probably already familiar with. It’s the kind that you did in PE class when you’re running around the track. Low intensity steady state cardio is usually categorized by being in like a 50 to 65% of your maximum heart rate range. Now what that means is that you’re not at a very high intensity. You’re at just enough to be breathing heavily, probably can carry on a conversation, maybe running on the treadmill, running around the track for 20, 30, 40, 50, 60, up to two hours, whatever. You’re just running, you’re getting activity going. It could be elliptical, it could be stationary bike. That’s just low intensity steady state cardio. Now what ends up happening is during low intensity steady state cardio, you’re burning more fat as a fuel source. It doesn’t literally mean that you’re burning more fat overall. It just means that your body burns fat as a fuel source.

Now I’ve talked about this in other videos but I’m trying to make this general because it’s the internet’s only HIIT versus LISS video. When you are working in a lower capacity like that, you’re working at a lower capacity, you’re in a situation where your body can utilize fat as a fuel source. You see, how it works is when you’re breathing oxygen, that oxygen comes in and oxygen combines with fat to create energy, but it can only do this at a low speed. Once you start going faster and you’re not low intensity anymore, your body can’t keep up. You see, it’s a very slow process of breathing in air, extracting the oxygen, combining it with fat, and actually creating energy. Once you start and you start going into high intensity interval stuff, you’re going into a whole different system because your body can’t keep up, so it has to start using carbs instead of oxygen plus fat. We’ll get to that in a second. So that’s why advocates of the low intensity steady state cardio are always saying that LISS is better, because they’re saying, “Well, you’re in this fat burning zone. You’re in the fat burning zone that’s allowing you to just use fat as a fuel source.” If you’ve been to the gym and you’ve seen those little charts that they have, they say aerobic zone, fat burning zone, high intensity zone, all that? That’s exactly what they’re talking about.